The present invention relates to information-processing apparatus, an information-processing method adopted by the information-processing apparatus, a program implementing the information-processing method and recording mediums for storing the program. More particularly, the present invention relates to information-processing apparatus properly used for recording data onto recording media for recording data sequentially as well as relates to an information-processing method adopted by the information-processing apparatus, a program implementing the information-processing method and recording mediums for storing the programs.
As the conventional data recording/reproduction apparatus capable of recording digital data onto a magnetic tape and reproducing digital data from the magnetic tape, a tape streamer drive is commonly known. A magnetic tape of a tape cassette mounted on the tape streamer drive as recording media can have a very large recording capacity of about several tens to several hundreds of GB (gigabytes). Thus, for example, such a tape cassette is widely used as a backup for data stored in a hard disk of a host computer or used in formation of an archive from video data having a large amount, moving-picture data having a large amount or the like. For more information, refer to Japanese Patent Laid-open No. Hei 9-134256, which is used in this specification as patent document 1.
In the tape streamer drive described in patent document 1, an SCSI (Small Computer System Interface) interface is used in data input and output operations. That is to say, in an operation to record data onto a magnetic tape of a tape cassette mounted on the tape streamer drive, data is transferred from a host computer in recording units each having a typical size of 32 Kbytes and supplied to the tape streamer drive by way of the SCSI interface. Then, the data supplied to the tape streamer drive is compressed and, if necessary, subjected to processing such as a buffering process, a modulation process and an RF amplification process before being supplied to a magnetic head for writing the data onto the magnetic tape. In an operation to read out data from the tape cassette, on the other hand, the data read out by the magnetic head is demodulated and, if necessary, subjected to processing such as a buffering process to be followed by a decompression process before being supplied to the host computer.
In addition, the tape cassette has a non-volatile memory referred to as an MIC (Memory in Cassette) for storing data received from a memory controller employed in the tape streamer drive. The memory controller employed in the tape streamer drive is also capable of reading out data from the non-volatile memory. In addition, an SCSI command can be used to exchange information between the host computer and the non-volatile memory. It is thus necessary to provide for example a serial data bus independent of the SCSI interface between the host computer and the non-volatile memory.
Various examples of the host computer using the tape steamer drive to create a backup of data or an archive include a mainframe computer and an ordinary personal computer.
Examples of a file format adopted in a process to record data onto a magnetic tape during the era of wide use of mainframe computers include a magnetic tape format with an attached ANSI (American National Standards Institute)/JIS label and a magnetic tape format with an attached IBM label. JIS-SX-0601, which is one of these magnetic tape formats, prescribes an operation to record data onto a magnetic tape by repetition of a label and a file main body. The file label includes a file name consisting of up to 17 characters. The format prescription also includes formation of a file and classification by record fixed length and record variable length.
The magnetic file formats include the formats of files, which cannot be recorded onto a magnetic tape without the need for the user to become accustomed to driving and/or control of the tape, that is, files unrecordable onto the magnetic tape as they are. Examples of such a file are an ISAM (Indexed Sequential Access Method) file and a VSAM (Virtual Storage Access Method) file. In data construction such as construction of fixed rows, the data of these formats cannot be recorded onto the magnetic file as it is.
Contemporary file formats widely used at the present time include a file format referred to as a sequential-file format, which allows data to be recorded onto a magnetic tape directly. In UNIX (a registered trademark), for example, the file system itself treats recording mediums such as a disk and a magnetic tape as a single byte stream without distinguishing the recording mediums from each other. For operations such as formation of data recorded on a magnetic tape in a file system, however, an application program such as a tar (tape archiver) is set.
In addition, in an interface between the conventional tape streamer drive and the host computer, a set of logical commands on an application layer is a command set obtained by correcting and extending a set of commands for making random accesses to an HDD or the like into a set of commands for the tape streamer drive. The application layer is not a physical or transport layer, which can be electrically connected to others. Instead, the application layer is a layer prescribing, among others, the set of logical commands.
Typical interfaces between the conventional personal computers and peripheral apparatus include the SCSI (Small Computer System Interface), ATA (AT Attachment) and ATAPI (ATA Packet Interface) The SCSI interface is used mainly as a system interface for connecting a peripheral apparatus conforming to ANSI (American National Standards Institute) specifications to a personal computer. Examples of the peripheral apparatus are an HDD (hard disk drive), an MO (Magneto Optical) drive and a CD-R drive, which are externally connected to the personal computer. The ATA interface is the formal specification name of an IDE (Integrated Drive Electronics) interface used mainly as an interface with an HDD, which conforms to the ANSI specifications as described above. The ATAPI interface is a packet interface devised as an interface for connecting an IDE controller to a device other than a hard disk. An example of the device other than a hard disk is a CD-ROM. In comparison with the IDE interface, the ATAPI interface improvement of the transfer speed, support for removable media, functions for portable PCs and others are prescribed in specifications. Since the ATAPI interface is capable of converting an SCSI command into an ATA command, by using the ATAPI interface, relatively with ease, it is possible to develop a CD-ROM drive, which does not require an expensive SCSI interface.
An extended command set for operations to record data onto a magnetic tape and reproduce data from the tape is defined for each of these interface specifications. By using these command sets, it is possible to treat data to be recorded onto the magnetic tape as a single data stream, issue commands to position a magnetic head and read out data or write data at the address of any block, the address of any byte, at any file mark or any set mark with the start position of the magnetic tape or the present position of the magnetic head taken as a reference.
That is to say, in the specifications of interfaces such as SCSI, ATA and ATAPI, which are mainly used as the conventional interfaces between a personal computer and peripheral apparatus, there is no concept of a data unit used as a file or a folder in the host computer. In addition, the tape streamer drive carries out an operation to record data onto a magnetic tape and read out data from the magnetic tape without having the concept of a data unit used as a file or a folder in the host computer.
The formats of a file of data to be recorded onto a magnetic tape are prescribed by an application program. Since the application program is executed in the host computer, the program is consciousness of a data unit used as a file or a folder in the host computer. The prescribed formats include a format prescribing tar (Tape Archiver) commands for typically Microsoft Windows (a trademark), an MTF (Microsoft Tape Format) prescribed by NT and a UNIX (a registered trademark) format. The tar commands do not have a compression function. However, the tar commands are commands for collecting a plurality of files into a single one or restoring data to an archived file and transmitting the single file.
While the tape streamer drive is characterized in that the magnetic tape accommodated therein can have a large storage capacity, the drive raises a problem that time it takes to position the magnetic head during recording and reproduction operations is long.
In the tape streamer drive, it may be impossible to know the substance of data recorded on the magnetic tape of a tape cassette mounted on the drive unless the identifier of a file recorded on the tape along the data is fetched. In many cases, an identifier is recorded at the beginning of each data recorded on the magnetic tape. For this reason, in order to read out desired data from a location on a magnetic tape employed in a tape cassette mounted on the tape streamer drive or record data onto a location on the tape, the user needs to make an access to the location by scanning data already recorded on the tape from the beginning of the tape. Thus, in comparison with, for example, an HDD allowing a random access to be made by virtue of a directory information area allocated to the file system, time it takes to make an access to desired data is long.
In order to solve the above problem raised in an access to a location on a magnetic tape employed in a tape cassette mounted on the tape streamer drive, the host computer holds a catalog in typically a backup utility included in Windows (a registered trademark) as a utility named NTBAKUP.EXE. The catalog is information such as indexes or a directory. By using the catalog, the host computer controls the tape streamer drive in operations to read out data from the magnetic tape and write data onto the tape. That is to say, the host computer holds file information of data recorded by the tape streamer drive on the magnetic tape.
Since the magnetic tape is a removable recording medium, it may be mounted on a host computer other than the host computer holding the file information. In this case, when the other host computer reads out data from the magnetic tape or writes data onto the tape, the computer needs to scan the magnetic tape in order to create the catalog. This is because the host computer does not hold a catalog. The larger the storage capacity of the magnetic tape, the longer the time it takes to scan the tape in order to create the catalog.
As described above, it is the host computer that controls operations carried out by the tape streamer drive. Thus, it is difficult to reduce the number of damages inflicted on the magnetic tape and shorten the access time by optimizing the operations of the tape streamer drive independently of processing carried out by the host computer.
In addition, in many cases, the tape streamer drive is used as means for creating a backup or archive of data on the magnetic tape. That is to say, in an operation to write data onto the magnetic tape in a backup or archive process, the data already exists as a complete file on a hard disk employed in the host computer. Thus, for example, attributes such as the name and size of the file have been determined. In an operation carried out by the conventional tape streamer drive to record data onto the magnetic tape or reproduce data from the tape, however, attributes such as the size of a file cannot be utilized in controlling the operation.